A garage conversion turns an existing garage into a legal living unit. Because the foundation, walls and roof are already there, it is often the least expensive way to add a full ADU, provided the structure is sound enough to reuse.
Do setbacks apply to a converted garage?
Not to the existing structure. As of October 2026, state law does not require a setback for an ADU created within an existing structure or rebuilt in the same location and dimensions. That matters for older San Diego garages built close to the side or rear property line.
Can the conversion get a little bigger?
A little. As of October 2026, the HCD Handbook says ADUs converted from accessory structures can expand by up to 150 sq ft, limited to what is needed for ingress and egress, such as a stair or entry. Larger additions are treated more like new construction.
Will I have to replace the parking?
No. As of October 2026, state law says parking lost when a garage is converted or demolished for an ADU does not have to be replaced. Plan for where cars and storage will go instead.
What usually needs fixing in a San Diego garage?
- a new or leveled slab, or a moisture barrier over the existing one
- repairs for termite damage or dry rot in framing and roof sheathing
- insulation, drywall and windows that meet egress and energy rules
- infill of the garage door opening with a wall, window or entry
- new plumbing to the sewer line and electrical capacity for a kitchen
- fire separation from the main house when the garage is attached
What does a garage conversion cost in San Diego?
As of October 2026, local contractors publish ranges of about $100,000 to $225,000. The garage's condition is the swing factor. Compare it with a new build in garage conversion or new ADU.
Should an attached garage become a junior ADU?
Sometimes. An attached garage can become a junior ADU of up to 500 sq ft with an efficiency kitchen, or a full attached ADU with its own bathroom. Which fits depends on its size and how you want the space to connect to the house.